DESCRIPTION (applicant's abstract): Neonatal maternal deprivation in the rat leads to depressive-like symptoms, including behavioral and neuroendocrine hyper-responsiveness to psychological stressors. This proposal asks whether transient and/or long-term changes in the anatomy and/or function of the hippocampus occur as a result of neonatal maternal deprivation. Numerous studies have linked both neonatal and adult exposure to elevated levels of glucocorticoids and/or stress with hippocampal dysfunction, including changes in neuronal morphology and number and cognitive function. Neonatal maternal deprivation has been demonstrated to accentuate the pituitary-adrenal responsiveness to stressors which may, in part, be the result of decreased expression and binding of glucocorticoid receptors in the hippocampus, a target for negative feedback by glucocorticoids on the stress response. Glucocorticoids regulate both neurogenesis and apoptosis in the dentate gyrus of the hippocampus of adult and neonatal rats. This study asks whether elevated levels of glucocorticoids due to maternal separation alter granule neuron number, genesis, apoptosis, morphology and spatial learning.